Merck today has jumped into what has become one of the hottest areas in oncology, antibody-drug conjugates, through a deal with San Diego-based Ambrx. Merck will pay $15 million upfront and up to $288 million in milestones for access to Ambrx’s site-specific protein conjugation technology. Coincidentally, on the cover of today’s magazine, we take a look at the future of antibody-drug conjugate technology. Although people have been working on ADCs for three decades, interest in the approach has reached fever pitch after last year’s approval Seattle Genetics’ lymphoma drug Adcetris and the recent hubbub at ASCO over positive interim Phase III data for Genentech’s T-DM1. The idea behind ADCs is simple: use a targeted antibody to deliver a highly potent chemotherapeutic to a cancer cell, sparing healthy cells. But current ADC technology has limitations. This week’s cover story looks at efforts to improve upon each component—the antibody, the small molecule, and the “linker” that connects the two. Ambrx is focused on the antibody, using site specific protein conjugation technology to better control how many and where small molecules are placed on an antibody. Currently, companies manufacturing ADCs (most using technology from Seattle Genetics or ImmunoGen) wind up with a heterogenous product—each ADC has anywhere from zero to eight small molecules attached to the protein, but on average, 3.5 to four small molecule “payloads” linked. The placement of the payloads on the antibody also varies, leading to families of conjugates. As I explain in today’s story, even among the ADCs with four small molecules attached, some have all the cytotoxins clustered in one region, but they might be spread out on others. Ambrx incorporates a nonnatural amino acid into the antibody to allow precise placement of the drug payload. As I explain: Ambrx can insert p-acetyl-phenylalanine onto two sites of the antibody. The phenyl- alanine derivative has been modified to include a ketone that acts as a functional group for conjugation to the linker and small molecule. Although Ambrx can attach more than two chemistry “handles” to the antibody, its studies have shown that two small molecules make the most sense. “You really want to be mindful about preserving the native structures and function of the antibody, while trying to optimize therapeutic activity,” says Chief Technology Officer Ho Cho. “The more you stray away from that, the more risks there are in drug development.” The beauty of site-specific conjugation, researchers say, is that it allows them to me- thodically determine which ADC variety is the most active. “We can specifically attach whatever payload-linker combo we wish and do quantitative experiments to find out how it works,” Cho says. His team...

Cambridge, Mass.-based Epizyme has scored $90 million upfront as part of a broad cancer drug development pact with Celgene. The deal adds to a spate of lucrative pacts to find compounds to modulate epigenetic targets, or enzymes that control gene expression without altering the underlying DNA. As we wrote in last week’s cover story, DNA carries the instructions for assembling all of life’s essential building blocks, but epigenetics dictates how and when that DNA is put to work. Recently, companies have made significant process in understanding the complex biology behind epigenetic processes, while also figuring out how to design compounds that can potently block epigenetic enzymes. With the science and business rationale for pursuing epigenetic targets dovetailing, big pharma and big biotech alike are forging deep ties with the handful of companies with expertise in the field. Under the three-year deal announced today, Celgene has the right to opt-in to the ex-U.S. rights for any unencumbered histone methyl transferase program at Epizyme. Eisai currently has the rights to Epizyme’s EZH2 inhibitor, while GlaxoSmithKline has a deep collaboration with Epizyme against undisclosed targets that would be excluded from today’s pact with Celgene. Epizyme says the partnership makes sense because Celgene shares “our vision in oncology and epigenetics,” says Epizyme’s president and CEO Robert J. Gould. “That’s been a fundamental bedrock of our partnering strategy–to partner with people who share our enthusiasm for this space.” Indeed, Celgene has long played in the epigenetics space, boasting two of the four currently marketed drugs that act on epigenetic targets. However, Celgene’s drugs, Istadax and Vidaza, hit first-generation epigenetic targets. Epizyme’s activities, meanwhile, center on one of the next waves of epigenetic targets: a family of enzymes called histone methyltransferases (HMTs). Of the 96 members of that family, Epizyme has identified roughly 20 HMTs for which there is a clear link to a specific form of cancer, Gould says. To date, the company has two compounds—the EZH2 inhibitor partnered with Eisai, and a DOT1L inhibitor—in preclinical studies. (Check out last week’s cover story on epigenetics for more on how Epizyme went about discovering those two compounds.) Celgene is kicking off the pact by opting into the inhibitor of DOT1L, an HMT that is implicated in mixed lineage leukemia, a rare subtype of the blood cancer that the Leukemia and Lymphoma Society says affects about 1,500 new patients in the U.S. each year. With each program thereafter that Celgene buys into, Epizyme could score up to $160 million in milestone payments. The cash influx, coupled with the U.S. rights to the programs, “positions us nicely to maintain our independence, but also control our own future as a...

You know you’re at an interesting conference when the director of the NIH starts off his presentation with a guitar duet, and shares a session with Cookie Monster. But the organizers of TEDMED made a very deliberate decision in opening this year’s conference with Francis Collins. This is the first year that the gathering of medical luminaries, artists, and design gurus (TED stands for Technology, Entertainment, Design) is taking place in Washington, DC, after moving from San Diego. It marks a philosophical shift for the organization, from TEDMED as idea incubator to TEDMED as inserting itself into the national conversation on health and medicine. What better way to do that then bringing in the head of the biggest biomedical funding agency? Collins wants to compress the time it takes to get a drug development pipeline, and make the pipeline less leaky. This isn’t news to folks around the pharma blogosphere, including here at the Haystack, Ash at Curious Wavefunction and Derek Lowe, who’ve followed last year’s announcement of NIH’s venture for drug discovery, the National Center for Advancing Translational Sciences. Folks have expressed some concerns about the concept, and its emphasis on the promise of gene-based drug discovery. But, as Derek noted, the fact of the matter is that everyone in drug discovery wants the things Collins wants, so there’s a measure of goodwill for the venture too. Collins spent his time on the TEDMED stage emphasizing two things: drug repurposing and developing high-tech cellular solutions to supplement and replace often-imperfect animal models. On the tech side, Collins showcased the Harvard-based Wyss Institute’s lung-on-a-chip, which combines tissue engineering and electronics to mimic the interface between the lung’s air sacs and capillaries (Science, DOI: 10.1126/science.1188302). He said that technologies like this suggest viable alternatives to animal testing are possible. When New Scientist reported on the lung-on-a-chip in 2010, researchers praised it as a step in the right direction, but cautioned that immortalized cell lines, such as those on the chip, don’t neccesarily behave like primary cells from patients. Collins also noted that it might be possible to use such devices with patients’ own cells someday. On the repurposing side, Collins cited an article on the topic in Nature Reviews Drug Discovery (DOI: 10.1038/nrd3473), and alluded to lonafarnib (SCH 66336), a farnesyltransferase inhibitor that was originally designed to be part of cancer-treatment cocktails. It didn’t pan out as a cancer drug, Collins said, but now clinical trials are underway to test whether the drug is effective at countering a rare mutation that causes Hutchinson-Guilford progeria, an ailment that leads to rapid aging in children. Collins shared the stage with 15-year-old Sam,...

Yesterday brought word of a new partnership between Merck & Co. and Scripps Research Institute chemist and biotech entrepreneur Peter Schultz. The two have launched the California Institute for Biomedical Research (Calibr), a San Diego-based not-for-profit that will collaborate with academic investigators to bring drug discovery ideas to the point of proof-of-concept in animals. Merck has kicked in $90 million over seven years to help fund the venture, and will have an option to license any molecule that comes out of it. C&EN’s news story with all the nitty-gritty details can be found here, but we wanted to follow up with some more insights into the formation of the institute gleaned from talks yesterday with Schultz and Merck’s R&D head Peter Kim. A burning question I had was how the individual collaborations with academic researchers would be structured. Throughout my coverage of pharma-academia collaborations over the years (see here and here), I’ve repeatedly heard from big pharma that a major hang-up in doing more and better deals is the difference of opinion between the company and the university tech transfer office in the value of an early stage project. Drug companies will say a discovery needs a lot of work, done on their dime, and a university wants to ensure it gets its fair share of the potential sales of a drug. One benefit of the not-for-profit as intermediary model is that the set up sidesteps what can quickly become contentious negotiations between universities and potential industry partners, Schultz says. “When it gets to a discussion between a university tech transfer office and big pharma, all of a sudden it’s ‘who’s taking advantage of whom’,” Schultz says. Conversely, “it’s really easy for people at, say, UCSF and Berkeley to collaborate.” At Calibr, the collaboration begins at such an early stage in the discovery process that it offers a straightforward 50/50 split in any gains made down the road. “The whole idea of two not-for-profits with complementary skill sets in a collaboration is to make it simple and move things forward,” Schultz says. Based on early conversations Schultz and others involved with Calibr have had with potential collaborators, that model seems satisfactory. “People get it,” he adds. Another question was how quickly Calibr will move forward. Despite a lot of talk of eliminating red tape in some of the more ambitious pharma-academia collaborations, getting things up and running when two different flavors of bureaucracy are involved is no small task. Schultz says that the first projects to come through Calibr will likely be a result of networking by the institute, its scientific advisory board, and Merck. He expects they will...

BMS is shelling out $2.5 billion dollars for Inhibitex, a small pharma company with a Phase II molecule for treatment of Hepatitis C (HCV). The deal adds to the scramble for HCV assets in recent months, with Gilead agreeing to pay almost $11 billion for Pharmasset in November, and Roche’s recent purchase of Anadys. While much has been written about the merits (and price tags) of each deal, the Haystack thought it was worth taking a closer look at the chemical composition of the multi-million dollar molecules. So what did BMS get for their money? INX-089, Inhibitex’s lead molecule, has a common antiviral motif: a nucleoside core (the 5-membered ring sugar attached to a nitrogen heterocycle) with an amino acid based prodrug hanging off the left-hand side. Clinically-tested antivirals sharing this basic setup include IDX-184 and NM-283, both from Idenix, and PSI-352938, from Pharmasset (For an overview of the varied structures currently in development for HCV, see Lisa’s 2010 C&EN story). INX-089 bears a close resemblance to Pharmasset’s lead nucleotide inhibitor PSI-7977. That’s not a mistake, believes ‘089 discoverer Chris McGuigan, of the Welsh School of Pharmacy. In a recent article (J. Med. Chem. 2010, 53, 4949), McGuigan himself comments “The Pharmasset nucleoside [is] rather parallel to our early work on anti-HIV ProTides.” Wait, what are ProTides? Both INX-089 and PSI-7977 aren’t themselves the active viral inhibitor, but phosphoramidate “ProTide” prodrugs: compounds broken down by the body into the active drug (Chem Note: PSI-7977 has single-enantiomer Sp chirality at phosphorus, while INX-189 is a mixture of diastereomers). Once in the body, enzymes cleave the phosphoramidate group to a phosphate (PO42-). Kinases attach two more phosphate groups, and viruses let this dressed-up molecule inside, where the nucleotide warhead inhibits HCV by interfering with RNA replication (Antimicrob. Agents Chemother. 2011, 55, 1843). A few comments on the drug itself: The similarity of the ProTide portion (left-hand side) of the molecule to PSI-7977 really is striking: swap in an isobutyl ester and a phenyl, and it’s the same beast! The more interesting switch comes on the upper-right (“eastern”) part of the structure: a protected guanosine ring. This ring harks back to guanine, one of the four common nucleic acids found in DNA. PSI-7977, meanwhile, shows off a uracil, a nucleic acid found in RNA, not DNA. Although it’s tempting to think such similar compounds all dock into the NS5B polymerase at the active site (in the yellow “palm” of the hand-shaped enzyme), don’t be too sure – a recent paper by Pharmasset scientists (J. Med. Chem. 2012, Just Accepted) shows quite a few “Finger,” “Palm,” and “Thumb” sites. It’s not yet clear whether...

Well, 2011 is in the books, and we here at The Haystack felt nostalgic for all the great chemistry coverage over this past year, both here and farther afield. Let’s hit the high points: 1. HCV Takes Off – New treatments for Hepatitis C have really gained momentum. An amazing race has broken out to bring orally available, non-interferon therapies to market. In October, we saw Roche acquire Anadys for setrobuvir, and then watched Pharmasset’s success with PSI-7977 prompt Gilead’s $11 billion November buyout. And both these deals came hot on the heels of Merck and Vertex each garnering FDA approval for Victrelis and Incivek, respectively, late last spring. 2. Employment Outlook: Mixed – The Haystack brought bad employment tidings a few times in 2011, as Lisa reported. The “patent cliff” faced by blockbuster drugs, combined with relatively sparse pharma pipelines, had companies tightening their belts more than normal. Traffic also increased for Chemjobber Daily Pump Trap updates, which cover current job openings for chemists of all stripes. The highlight, though, might be his Layoff Project. He collects oral histories from those who’ve lost their jobs over the past few years due to the pervasive recession and (slowly) recovering US economy.. The result is a touching, direct, and sometimes painful collection of stories from scientists trying to reconstruct their careers, enduring salary cuts, moves, and emotional battles just to get back to work. 3. For Cancer, Targeted Therapies – It’s also been quite a year for targeted cancer drugs. A small subset of myeloma patients (those with a rare mutation) gained hope from vemurafenib approval. This molecule, developed initially by Plexxikon and later by Roche / Daiichi Sankyo, represents the first success of fragment-based lead discovery, where a chunk of the core structure is built up into a drug with help from computer screening.From Ariad’s promising ponatinib P2 data for chronic myeloid leukemia, to Novartis’s Afinitor working in combination with aromasin to combat resistant breast cancer. Lisa became ‘xcited for Xalkori, a protein-driven lung cancer therapeutic from Pfizer. Researchers at Stanford Medical School used GLUT1 inhibitors to starve renal carcinomas of precious glucose, Genentech pushed ahead MEK-P31K inhibitor combinations for resistant tumors, and Incyte’s new drug Jakifi (ruxolitinib), a Janus kinase inhibitor, gave hope to those suffering from the rare blood cancer myelofibrosis. 4. Sirtuins, and “Stuff I Won’t Work With – Over at In the Pipeline, Derek continued to chase high-profile pharma stories. We wanted to especially mention his Sirtris / GSK coverage (we had touched on this issue in Dec 2010). He kept up with the “sirtuin saga” throughout 2011, from trouble with duplicating life extension in model organisms to the...

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